This invention relates to plasma treatment of an article and, in particular, to plasma enhanced chemical vapor deposition (CVD).
The use of plasma reactors for various etching processes is well known in the art. Also known, but less frequently exploited, is the use of plasma reactors for deposition, e.g. a conductive or insulating layer on a semiconductor wafer. While the advantages of planar plasma reactors are well known, e.g. U.S. Pat. No. 4,223,048, they are not free from problems. Some problems are inherent in the process itself. For example, silane (SiH.sub.4) deposits silicon everywhere, once a minimum temperature is reached. The contamination problems are obvious. Silicon tetrachloride (SiCl.sub.4) will not deposit silicon by itself and has a higher minimum deposition temperature. Intermediate compounds, e.g. dichlorosilane (SiH.sub.2 Cl.sub.2), have intermediate characteristics. Thus, one is faced with the problem of switching or mixing gases during a process, yet trying to obtain consistent results.
Another source of difficulty, in a sense, is the semiconductor industry itself. There is a constant demand for better results, e.g. uniformity, through-put, deposition rate. Improving both uniformity and deposition rate, for example, is not easy. Further, there are several kinds of uniformity. A first relates to the wafer itself. A second concerns from wafer to wafer in a given batch. A third kind relates to uniformity from batch to batch. For single wafer plasma reactors, the latter two are the same since the wafers are processed singly. As can be seen, improving one parameter may not be particularly difficult. Improving all of them is a feat.
Another consideration is the increased use of automation. As known, it is highly desirable to process a plurality of wafers at a time in a vacuum. Thus, vacuum load locks and vacuum transports are being used more frequently. This leads to the desire to process wafers more quickly, e.g. at higher deposition rates, to match more closely the increased speed of the wafer transports. Thus, not only must the process be improved, but the chamber in which the process takes place must be compatible with vacuum load locks and transports as well.
In view of the foregoing, it is therefore an object of the present invention to provide improved plasma deposition apparatus.
Another object of the present invention is to provide an improved plasma deposition process in which both deposition rate and uniformity are improved for single wafer deposition in an automated vacuum load lock convertible for wafer diameters of 3-10 inches.
A further object of the present invention is to provide improved means for heating a semiconductor wafer.
A further object of the present invention is to provide improved means for controlling gas flow in a deposition chamber.
Another object of the present invention is to provide improved temperature sensing means for deposition apparatus.
A further object of the present invention is to provide improved control means for radiantly heating a wafer.
Another object of the present invention is to provide a process chamber compatible with vacuum transport apparatus.